U.S. Pat. No. 8,057,535 discloses a conventional electrospinning device 1 as shown in FIG. 1. The electrospinning device 1 includes a mandrel 11, a spinneret 10 for dispensing a polymer fluid, and a reservoir 12 for holding the polymer fluid. The mandrel 11 can be driven to rotate, and the spinneret 10 can reciprocate along a longitudinal direction of the mandrel 11 to create a layer of polymer fibers on the mandrel 11. However, because the speed of the reciprocating movement of the spinneret 10 is not sufficient to enable the polymer fibers to be arranged along the longitudinal direction of the mandrel 11, and because the spinneret 10 is likely to vibrate during the reciprocation thereof, the polymer fibers have a poor orientation along the longitudinal direction of the mandrel 11.
Another conventional electrospinning device 2 is shown in FIG. 2, and has been disclosed in an article entitled “Electrospinning of small diameter 3-D nanofibrous tubular scaffolds with controllable nanofiber orientations for vascular grafts” (J. Mater. Sci.: Mater. Med. (2010) 21:3207-3215). The electrospinning device 2 includes a motor 20, an electro-insulator Teflon rod 21, two metallic plates 22, and a spinneret 23. The two metallic plates 22 are separately placed. The electro-insulator Teflon rod 21 has two segments disposed respectively and rotatably on the metallic plates 22 as a collector of electrospun nanofibers and is driven to rotate by the motor 20. When the metallic plates 22 are connected to a DC negative voltage power supply and a high voltage is applied to a polymer solution in the spinneret 23, electrospun nanofibers of axial orientation can be formed on the Teflon rod 21 by regulating the electric fields through the two separately placed metallic plates 22. After removal of the Teflon rod 21, an electrospun 3-D nanofibrous tubular scaffold is obtained. In the electrospinning device 2, since the two metallic plates 22 are spaced apart by a relatively small distance in order to produce the electrospun nanofibers of axial orientation, the 3-D nanofibrous tubular scaffold has a limited length.